Induction heating is a method of heating a workpiece. Induction heating involves applying an AC electric signal to a conductor adapted to produce a magnetic field, such as a loop or coil. The alternating current in the conductor produces a varying magnetic flux. The conductor is placed near a metallic object to be heated so that the magnetic field passes through the object. Electrical currents are induced in the metal by the magnetic flux. The metal is heated by the flow of electricity induced in the metal by the magnetic field.
Typically, induction heating is performed by a large fixed system located in a manufacturing facility, such as a foundry. Systems have been developed for performing induction heating on location at a worksite. However, these systems are very limited in their abilities. For example, existing induction heating systems for use on-site are not designed to perform temperature profiling of a workpiece, as is required for certain induction heating operations, such as post-weld stress-relieving. Temperature profiling is a process whereby a number of heating and/or cooling operations are performed on a workpiece over a period of time. The workpiece may be heated at a specific rate to a specific temperature, maintained at that temperature for a specified period of time, and then lowered at a specific rate to a lower temperature. Heat may still be provided to the workpiece during cooling so as to control the rate of temperature decrease. Materials of different size may require the induction system to operate at different temperatures and rates of temperature change. In addition, different operations may require that a workpiece undergo an entirely different temperature profiles.
There is a need therefore for an induction heating system that avoids the problems associated with current onsite induction heating systems. Specifically, there is a need for an on-site induction heating system that is operable to be programmed to perform a variety of induction heating operations including post-weld heating, stress-relieving, annealing, surface hardening, and other heat treating applications.